Final Project Evaluation
The Traffic Calming Program (TCP) undertook a streamlined speed bump project in the Fall of 1995 to address traffic problems identified by residents along SE Ankeny from 12th to 20th Avenue.
The goal of the project was to enhance street safety and livability by reducing the 85th percentile speed of vehicles using SE Ankeny closer to the legal maximum speed limit of 25 miles per hour (mph). Speed bumps are the only device considered for streets like SE Ankeny, which are classified as Local Service Streets, are not transit or primary fire response routes and have vehicle volumes between 400 and 1700 vehicles per day. Speed bumps have proven to be effective tools to reduce vehicle speed without impacting access. It is not an intended goal to reduce traffic volume on low-volume Local Service Streets.
SE Ankeny serves a mixed single family residence and apartment/commercial neighborhood. 12th Avenue, to the west, is a Major City Traffic street. 20th Avenue, at SE Ankeny's east end, is a Neighborhood Collector street. SE Ankeny has sidewalks and curbs. A portion of the daily traffic on SE Ankeny is believed to be cut-through traffic due to congestion on SE 12th Avenue.
All residents along SE Ankeny were invited to an open house January 9, 1996 to review and comment on the proposed speed bump installation. Ten people signed in at the open house. The majority of those who attended expressed approval for the proposed project. There was concern expressed about the size of the bumps. A petition was available at the open house for residents along SE Ankeny to sign and was circulated after the open house by a local resident. Of the 38 households along the street, 26, or 68.4%, signed the petition requesting speed bump installation.
Four 14-foot speed bumps, at 450 to 500 foot spacing, were constructed along the 0.38 mile stretch of SE Ankeny, 12th to 20th Avenue, on October 5, 1996 by the Bureau of Maintenance.
As the graph shows, vehicle speeds, previously concentrated between 20 and 28 mph, have been shifted into the range of 20 to 25 mph. The average 85th percentile vehicle speed before the project was 30.2 mph. After bump construction the average 85th percentile speed is 25.4 mph and ranges from a low of 21 mph (near the bumps) to a high of 28 mph.
Traffic volumes measured before bump construction averaged 1430 vehicles per day (vpd) and varied from 680 to 2600 vpd. Higher volumes were measured at the west end of the street. After bump construction volumes averaged 1100 vpd and varied from 630 to 2100 vpd, with higher volumes continuing near the west end. Traffic volumes measured on side streets adjacent to SE Ankeny showed no significant increases from volumes measured prior to speed bump construction.
Traffic Calming on SE Ankeny, 12th to 20th Avenue has successfully reduced the 85th percentile closer to the posted speed and enhanced street safety and livability.